Pneumatic timing device having straight through operation



Oct. 29, 1968 E. F. DUNCAN 3,408,465

PNEUMATIC TIMING DEVICE HAVING STRAIGHT THROUGH OPERATION Filed July 25,1966 3 Sheets-Sheet 2 Inna 1||m "II I 6 /5 /7 3- 53 g /8 54 T m) 59 26 r9 20 "2/ 43 I 29a 4 23\ II I I II I I 4 Oct. 29, 1968 E. F. DUNCAN3,408,465

PNEUMATIC TIMING DEVICE HAVING STRAIGHT THROUGH OPERATION Filed July 25,1966 5 Sheets-Sheet 5 34\ I 2/ v I 1l||l 1 5 14: 3 as 37 llllz i T ll--7a "HT T TLII HI ag. I I Z I HI United States Patent 3,408,465PNEUMATIC TIMING DEVICE HAVING STRAIGHT THROUGH OPERATION Eugene F.Duncan, Milwaukee, Wis., assignor to Cutler- Hammer, Inc., Milwaukee,Wis., a corporation of Delaware Filed July 25, 1966, Ser. No. 567,569 8Claims. (Cl. 20034) This invention relates to adjustable pneumatic timedelay devices and particularly to such devices to be used in conjunctionwith electrical switches such as limit switches.

Electrical limit swtches generally comprise a switch housing containinga precision snap action switch, and a multi-position operating headhaving either a rotary lever or top or side push type operator foractuating the switch contacts. The operating head assembly may beprovided with optional features such as overtravel means for theoperator, rotary and linear adjustment for the lever and variousmodified forms of levers as may be required according to the desired useof the switch.

In certain limit switch installations it is desirable to have a timedelay period between the operator movement and the controlling contactfunction. This may be accomplished through an auxiliary device such as atime delay relay mounted on a central control panel. However, the panelmay be some distance from the location of the limit switch and possiblyout of view of the switch. In this instance, an individual must makeblind adjustments to the timer and subsequently traverse the distancefrom the panel to the switch location to check his results, perhapsnecessitating several such adjustments and trips.

It is therefore an object of this invention to provide a timing devicewhich may be mounted to and function directly with a limit switch.

It is a further object of this invention to provide an adjustable timingdevice to be mounted to and function directly with a limit switchwhereby adjustments to the timing device may be made at the switchlocation.

It is a further object of this invention to provide an adjustable timingdevice for a limit switch which is mounted between the switch base andthe operating head of a standard limit switch whereby the timing featuremay be added to a switch having any or all of the other featuresdesigned therefor.

Another object of this invention is to provide an adjustable timingdevice which may be operated from one side to cause actuation of adevice on the opposite side thereof.

These and other objects will be more fully understood in the followingspecification and claims when read in conjunction with the accompanyingdrawings, wherein:

FIGURE 1 is a front elevational view of the timing device of thisinvention mounted to a limit switch which is shown in dotted lines;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1 showing anadjusting mechanism for the device;

FIG. 3 is a sectional view of the device taken along line 33 of FIG. 1showing the device in one operating condition;

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FIG. 8 is an enlarged fragmentary sectional view of a portion of themechanism shown in FIG. 2 drawn to an enlarged scale and taken along theline 8-8 of FIG. 9;

FIG. 9 is a fragmentary sectional view taken along line 99 of FIG. 8showing a feature of the adjusting mechanism and drawn to an enlargedscale;

FIG. 10 is a fragmentary sectional view taken generally along therotated line 1010 of FIG. 5; and

FIG. 11 is a sectional view similar to FIG. 3 showing a second preferredembodiment of the device.

As seen in FIG. 1, a timing device 2 is mounted between an operatinghead 3 and the base portion 4 of a standard limit switch having a rotarylever operator. The operating head 3 has a rotatable shaft 5 extendingoutwardly through one side to which is attached the operating lever 6.The operator 6 is adjusted to extend into the path of travel of a movingobject which will rotate the operator out of its path as it passes by.

Rotation of the shaft 5 by operator 6 causes a camming member within thehead to move a plunger 7a (FIG. 3), which extends into the timingdevice, toward the switch base 4. In the standard limit switch usedwithout the timing device the plunger 7a is in direct engagement with acontact carrier means as indicated by the dotted line 8 in FIG. 7 andthe described movement causes contact actuation of the switch 9 againstthe bias of return spring 10. Upon return of operator 6 to its originalposition the camming mechanism releases the plunger 7a and the spring 10causes the plunger to return to its initial position. When the timingdevice 2 is incorporated into the switch, the plunger 7a extends intothe device as shown in FIG. 3 and a second identical plunger 7b isprovided with the device to extend into the switch base 4 to engagecarrier means 8.

The joint between the operating head 3 and the base portion 4 of thestandard limit switch is provided with a diaphragm type of seal toprevent foreign material from entering the switch. In the switch of thisinvention a similar seal 11 is provided at the joint between theoperating head 3 and the timing device 2 and an identical seal 12 isprovided between the timing device and the base portion 4. The uppersurface of timing device 2 has an annular groove formed thereinidentically to the upper surface of the existing limit switch baseportion and these grooves receive the peripheral portions of seals 11and 12. A central aperture in each of the seals is received by a grooveformed in the respective plungers 7a and 7b to provide a sealed jointtherebetween. A small slit 11a and 12a is formed in seals 11 and 12,respectively, to prevent any build-up in air pressure on the outer sidesof the timing structure as will be seen later.

The timing device 2 comprises two housing portions, a cover member 13and a base member or valve body 14. The cover 13 has a central circularopening extending between' its upper and lower surfaces into which ispressed a bearing sleeve 15 to receive and guide plunger 7a. A pair offrusto-conical spring pockets 16 and 17 are formed in cover 13 whichopen to the bottom surface thereof. A transverse groove 18 (FIG. 4) iscut into the wall structures between the central opening and each of thespring pockets 16 and 17 and alined pairs of round ended slots 19 and 20are formed on opposite walls of the groove 18, the slots being open tothe bottom surface of cover 13 as shown most clearly in FIG. 10. Acircular recess 21 is also formed in the bottom surface of the covermember.

The base member 14 has a circular recess 22 formed in its uppersurfaces, which will become one surface and the sides of the timingchamber in later description, and another circular recess 23 formed inits lower surface. A circular central aperture extends between therecesses 22 3 and 23 and a bearing sleeve 24 is pressed into placewithin the aperture to receive and guide an intermediate plunger 25.

A diaphragm 26 is sealed along its peripheral flange between the lowersurface of cover 13 and the upper surface of base 14. With particularreference to FIG. wherein the diaphragm 26 is shown in its relaxedposition, the latter is provided with an annular oflset portion whichlies adjacent the periphery of recess 22 to provide flexure for movementof the central portion of the diaphragm which overlies the recess 22 tobecome the remaining surface of the timing chamber. A pair of largewashers 27 are provided on either side of the central portion of thediaphragm to provide that portion with a required rigidity. A centralclearance opening is provided in the diaphragm 26 and the washers 27 toreceive a screw 28 which takes into a threaded opening in plunger tosecure the plunger to the underside of the diaphragm assembly. Anannular ridge surrounding the central opening in diaphragm 26 iscompressed by the plunger 25 to provide an air tight seal between thetwo members.

The lower end of plunger 25 has an annular groove which receives asealing ridge surrounding a central opening in a flexible bellows 29made of rubber or the like. Bellows 29 has a flat, outwardly extendingannular flange portion 29a which is biased into and against a dishedarea in the upper surface of recess 23 by a closed-end helicalcompression spring 30 which bears against the flange 29a atapproximately its mean diameter and seals at its other end in a springretainer 31 pressed into the recess 23. Retainer 31 has a centralopening through which the plungers 25 and 7b may extend, the latterbeing maintained in engagement with plunger 25 by the bias of the switchreturn spring 10.

A lateral slot 32 extends along the opening for plunger 25 in base 14 tocommunicate with recesses 22 and 23 as seen specifically in FIGS. 5 and9. Slot 32 merges with a C-shaped groove 33 formed in the dished portionof recess 23 which is covered by the outer flange of bellows 29. Whenair is forced from the timing chamber due to a downward movement of thediaphragm 26 it passes through the slot 32 into the groove 33 and fromthere it is forced out between the flange 29a and the dished portion ofrecess 23. The flange 29a in this way functions as a one-way check valveallowing air flow in the above described direction and preventing airfrom returning into the timing chamber through the reverse path since areverse air flow at the outermost portion of the flange 29a would tendto increase the pressure of the flange against the dished area.

In order to provide equal air pressure above and below the timingchamber for achieving greater timing accuracy, a passageway is providedwhich communicates between recesses 21 and 23, shown specifically inFIG. 9. Cover 13 and base 14 are provided with alined holes 34 and 35,respectively, and a similarly alined hole is provided in the sealingflange of diaphragm 26. A hole 36 connects recess 21 to hole 34 and asimilar hole 37 connects recess 23 to hole 35, thereby providing adirect air passage between the two recesses.

The metering assembly to allow air to return into the timing chamber ata preset timed rate is shown specifically in FIGS. 2, 8 and 9. A squarehole 38 is formed in the base 14 open to one exterior side of the baseand terminating at the interior end in a minutely tapered frusto-conicalhole 39. An air intake opening 40 is formed in the base 14 to connecthole 38 with recess 23 and a similar opening 41 connects hole 39 withthe recess 22, or timing chamber. The side of base 14 through which hole38 extends is further provided with a circular recess 42 formedconcentric to the center of square hole 38. The recess 42 is in turnequally surrounded by a larger rectangular recess 43.

A metering pin 44, having a cylindrical body portion with an internallythreaded opening at one end, is pro- 4 vided at the other end with aconical end portion44a which is concentric with the hole 39. Thecylindrical body of pin 44 is further provided with a pair of offsettransverse slots, each of which receives a triangular bearing wedge 45.As seen in FIGS. 8 and 9, the wedges 45 are held outward against theopposite corners of hole 38 by the threaded shank of an adjusting screw46 which takes into the opening of metering pin 44. The shank of screw46 is exposed to the hypotenuse of eachwedge 45 by the slots in pin 44so that threads of the screw cut into each wedge to force the wedgesinto the opposite corners with sufiicient pressure to prevent the pinfrom rotating, yet allow the assembly to slide linearly along the holes38 and 39. The width of the slots and the wedges are held to a veryclose tolerance to provide extremely small clearance therebetween. Sincethe threads of the screw cut into the wedges, an immediate directionalresponse is afforded the pin upon rotation of the screw in eitherdirection to thus eliminate any lost motion as would be present throughthe backlash of the ordinary thread engagement. A washer 47 placed inthe circular recess 42 provides support for the free end of screw '46.'A cover plate 48 is placed in the rectangular recess 43 and held thereby screws 49. An 0 ring seal 50 is also placed in the recess 42 and iscompressed between the walls of the recess, the head of screw 46 and thecover plate 48 when the latter is secured in place, to prevent foreignmaterial from entering the timing chamber therethrough. Access to thehead of screw 46 is had through an'alined opening in cover plate 48,this opening further being covered by a pivotable member 51 held by oneof the screws 49.

Rotation of adjusting screw 46 in one direction causes the metering pin44 to thread itself upon the screw through the aforedescribed slot andwedge arrangement, thereby causing the conical end 44a thereof to slidelinearly outward with respect to the conical hole 39 and thus increasethe clearance between the hole 39 and the end 44a to allow a greaterpassage of air into the timing chamber. The reverse rotation of screw 46causes immediate reverse linear travel of end 44a with respect to hole39 to thereby decrease the clearance between the two and decrease thepassage of air into the timing chamber.

The seals 11 and 12 provide an eifective re-circulating air arrangementfor the timing device 2 upon its assembly to the limit switch. The slots11a and l2a allow for some air passage therethrough to prevent any greatpressure differential on opposite sides of the seals as may build upwithin the operating head 3 or switch base 4, while preventing foreignmaterial from passingtherethrough to interfere with the timingmechanism. In this regard, no extra air filtering assemblies arerequired since the air to be utilized for timing purposes remains withinthe timing device.

The operation of the device insofar as described may be seen withrespect to FIG. 10 wherein the device is shown in its inoperatedposition, there being a spacer sleeve 52 disposed around the screw 28between its head and the upper washer 27 of the diaphragm to raise thescrew into engagement with theplunger 7a in the latter inoperativeposition. Upon movement of the lever 6, the camming mechanism ofoperating head 3 causes plunger 7a to drive the central portion of thediaphragm assembly to a point very near the lower surface of recess 22to collapse the timing chamber and thereby exhaust the air thereinthrough the slot 32, groove 33 and out between the flange 29a of bellows29 and the dished portion of recess 23 as before described. The abovemovement also causes plunger 25 todrive plunger 7b toward thevswitchmechanism to simultaneouslyactuatethe switchcontagts 9. v I

p The return movement of the lever 6 to its original position causes thecamming mechanism to remove its force from the plunger 7a and hence thediaphragm 26.

The return spring of the switch mechanism then biases the diaphragm toits original relaxed position through plungers 7b and 25 against thevacuum created within the timing chamber. The diaphragm returns to itsoriginal position at a controlled rate due to the metered air intake tothe chamber through holes 40, 38, restricted hole 39 and opening 41,thereby affecting a time delay period between the release of theoperating lever 6 and the deactuation of the switch contacts 9.

When used as described above, the timing device is described in the artas off delay device. An on delay device may be provided within the samebasic timing device structure by the addition of certain parts ashereinafter described.

The pairs of alined slots 19 and of cover 13 receive pivot pins 53 and54, respectively. The pins are held against the closed ends of therespective slots by pairs of flathead screws 55 as shown in FIG. 4, thetapered heads of which engage conical end portions formed on the pins 53and 54. A pair of levers 56 and 57 straddle the pins 53 and 54,respectively, within the slot 18 at substantially their midportions topivot about the pins, the lever 57 being positioned reversely to thelever 56. The adjacent ends of the levers extend into the centralopening of cover 13 to engage the interior end of plunger 7a. Theopposite ends of the levers bear against the surface of the upper washer27 of the diaphragm. Helical compression springs 58 are placed in thespring pockets 16 and 17 to bias the levers against the washer 27through spring caps 59.

The timing device as just described is shown in FIG. 3 in its inoperatedposition, the lever 6 of the operating head and hence plunger 7a, beingin their normal position. In this position the springs 58 bias thelevers 56 and 57 to the position shown wherein the timing chamber iscollapsed and the adjacent ends of the levers engage the interior end ofthe plunger 7a in its inoperated position. The plunger applies aconstant force to the plunger 7b against the bias of spring 10 tomaintain the contacts 9 actuated.

Rotation of the lever 6 by a passing object operates the cammingmechanism to force plunger 7a inward, driving the adjacent ends of thelevers 56 and 57 downward which raises their opposite ends free of thediaphragm assembly and against the bias of springs 58. The bias ofreturn spring 10 urges the diaphragm to its relaxed position through theplungers 7b and 25 against the vacuum in the timing chamber. Air ismetered into the timing chamber through the metering pin assembly asbefore described to provide in this instance a controlled time delaybetween the operation of the operating lever and the deactuation of theswitch mechanism, known in the art as an on delay.

From the foregoing it may be seen that there is provided a timing devicewhich is adjustable, is capable of having either of two types of timedelay operations within identical superstructure, and which isrelatively inexpensive to manufacture and supply. In addition there isprovided a timing device having a centrally located straight throughoperating actuating mechanism which allows the superstructure to take onvarious forms to comply to the product to which it may be associatedwith to permit a building block, or modular structure. The device alsouses a substantially captive recirculating air supply which requires noexternal filtering assemblies for an outside air source.

It should be understood that the device as described and shown in theforegoing is merely exemplary of certain preferred embodiments and isnot intended to limit the scope of the appended claims.

I claim:

1. A pneumatic timing device comprising, in combination, a housinghaving a cavity therein, a flexible diaphragm secured along itsperiphery to said housing in sealed relation thereto and having acentral portion forming a chamber with a portion of said cavity in anormal position of said diaphragm, means biasing said central portion ofsaid diaphragm to said normal position, first and second openings insaid housing extending from said cavity to exterior surfaces of saidhousing and being on opposite sides of said diaphragm, a plunger membersecured to said central portion of said diaphragm within said chamberand extending through the first one of said openings, flexible sealingmeans providing an air-tight seal between said plunger and said firstopening and permitting reciprocable movement of said plunger within saidfirst opening, means extending through said second opening for causingmovement of said central portion of said diaphragm in one direction toeifect movement of said plunger within said first opening, one-way valvemeans permitting substantially unrestricted passage of air out of saidchamber upon movement of said central portion away from said normalposition, and metering means permitting air to enter said chamber at acontrolled rate upon movement of said central portion to said normalposition.

2. The combination according to claim 1, wherein said first and secondopenings in said housing are in axial alinement and movement of saidcentral portion of said diaphragm by said means extending through saidsecond opening in one side of said housing effects responsive movementof said plunger through said first opening in the opposite side of saidhousing.

3. The combination according to claim 2, together with lever meansmounted to said housing to engage said central portion of said diaphragmat one end thereof and said means extending through said second openingat the other end thereof, a second biasing means acting upon said levermeans for biasing said central portion of said diaphragm in onedirection, and wherein movement in one direction of said means extendingthrough said second opening causes movement of said lever means againstthe bias of said second biasing means to eflFect movement of saidcentral portion of said diaphragm and said plunger in a reversedirection.

4. The combination according to claim 2, wherein said one-way valvemeans in said flexible sealing means comprise a resilient bellows memberhaving a centarl opening to receive the outer end of said plunger insealed relation thereto and further having a peripheral flange whichlies along and closely conforms to a surface of said housing adjacentsaid first opening, together with a third biasing means to hold saidflange against said surface. s

'5. The combination according to claim 4, together with a switchoperating structure secured to said one side of said housing in sealedrelation thereto, a switch housing structure secured to said oppositeside of said housing in sealed relation thereto, and a passageway withinsaid housing extending between the areas on either side of said chamberfor providing equal air pressure on either side of said chamber.

6. The combination according to claim 5, wherein said metering meanscomprises a pasageway extending between said chamber and one of saidareas, and a tapered pin within a correspondingly tapered portion ofsaid passageway, said pin being adjustable within said portion toprovide a variable restriction in the air flow from said area into saidchamber.

7. The combination according to claim 6, wherein said metering meansfurther comprises an elongated opening of rectangular cross section openat one end to an exterior surface of said housing and terminating at itsother end in a frustoconical portion, a metering pin having acylindrical body portion terminating at one end in a tapered pin formedto be complemental to and concentric with said frusto-conical opening, athreaded opening in the other end of said cylindrical body portion toreceive an adjusting screw therein, the head of said screw beingassemble within said opening to said exterior surface, sealing means forproviding a seal between said screw and said opening, a plurality oftransverse grooves formed in said body portion, a plurality of wedgemembers seated within said grooves and having portions extendingoutwardly of said body portion to engage the walls of said rectangularopening for preventing rotation of said body portion within saidopening, whereupon rotation of said adjusting screw in one directioncauses said tapered pin to move -1inearly and non-rotatably into saidfrusto-conical opening toincrease the restriction of air flow into saidchamber.

8. The combination according to claim 7, wherein said wedge members aretriangular in shape, the hypotenuse 10 of which seats upon said screwwithin said groove and engages a bottom portion of said groove and theremaining edges thereof engage respective sides of said rectangularopening, and wherein there is provided at least 8 two of said wedgemembers oppositely disposed on said body portion, the apeces of whichengage vdiagonally opposite corners of said rectangular opening.

References Cited v UNITED STATES PATENTS' 3,246,094 4/1966 Zaske et a1ZOO-34 X 3,261,958 7/1966 Bittner 20034X ROBERT K. SCHAEFER, PrimaryExaminer.

HERMAN O. JONES, Assistant Examiner.

1. A PNEUMATIC TIMING DEVICE COMPRISING, IN COMBINATION, A HOUSINGHAVING A CAVITY THEREIN, A FLEXIBLE DIAPHRAGM SECURED ALONG ITSPERIPHERY TO SAID HOUSING IN SEALED RELATION THERETO AND HAVING ACENTRAL PORTION FORMING A CHAMBER WITH A PORTION OF SAID CAVITY IN ANORMAL POSITION OF SAID DIAPHRAGM, MEANS BIASING SAID CENTRAL PORTION OFSAID DIAPHRAGM TO SAID NORMAL POSITION, FIRST AND SECOND OPENINGS INSAID HOUSING EXTENDING FROM SAID CAVITY TO EXTERIOR SURFACES OF SAIDHOUSING AND BEING ON OPPOSITE SIDES OF SAID DIAPHRAGM, A PLUNGER MEMBERSECURED TO SAID CENTRAL PORTION OF SAID DIAPHRAGM WITHIN SAID CHAMBERAND EXTENDING THROUGH THE FIRST ONE OF SAID OPENINGS, FLEXIBLE SEALINGMEANS PROVIDING AN AIR-TIGHT SEAL BETWEEN SAID PLUNGER AND SAID FIRSTOPENING AND PERMITTING RECIPROCABLE MOVEMENT OF SAID PLUNGER WITHIN SAIDFIRST OPENING, MEANS EXTENDING THROUGH SAID SECOND OPENING FOR CAUSINGMOVEMENT OF SAID CENTRAL PORTION OF SAID DIAPHRAGM IN ONE DIRECTION OFEFFECT MOVEMENT